Abstract
α-Chloroheteroarylalkyllithiums generated by deprotonation of 2-(1-chloroalkyl)-heterocycles with n-BuLi in THF at –78 °C, were found to react as Darzens-type reagents with racemic and optically pure 2and 3-methylcyclohexanones. Heteroaryloxiranes containing new stereocentres were isolated in a diastereoand enantioselective manner.
Highlights
The deprotonation of α-chloroheteroarylalkanes with n-butyllithium (n-BuLi) or lithium diisopropylamide (LDA) at –78 °C in THF, provides carbanions relatively stable due to the presence, in their framework, of an aza heterocycle in α position and an adjacent electronegative chlorine atom, which add a further electron-withdrawing effect.[1]
An interesting diastereoselectivity has been observed in the coupling reaction of the above carbanions with carbonyl or iminic compounds affording oxiranes and aziridines, respectively.[2]
It has been reported that the coupling reaction of lithium azaenolates of chiral oxazolines with carbonyl compounds[6] produces asymmetric induction leading to chiral oxiranes
Summary
Abstract α-Chloroheteroarylalkyllithiums generated by deprotonation of 2-(1-chloroalkyl)-heterocycles with n-BuLi in THF at –78 °C, were found to react as Darzens-type reagents with racemic and optically pure 2- and 3-methylcyclohexanones.
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